The invention generally relates to earphones, in particular, in-the-ear earphones, designed to provide noise attenuation.
There are at least three headphone design types, which are generally categorized in terms of how they are worn by the user. The three design types are referred to as around-the-ear, on-the-ear, and in-the-ear headphones. Around-the-ear headphones have large earphones that resemble earmuffs. Like earmuffs, the around-the-ear earphone covers and surrounds the ear. It typically provides very good noise attenuation but it is not particularly comfortable, especially for people using eyeglasses. Since the earphone surrounds the user""s ear, it cuts off air circulation behind the ear and thus can be uncomfortably warm in hot weather.
In addition, under some circumstances such as when intelligibility of local conversation is important, the high level of passive attenuation provided at high frequencies by the around-the-ear headphones will cause intelligibility of external stimuli to suffer. There are many environments or applications in which it is desirable to hear external conversation or sound, for example, in certain industrial applications and in airplanes. In large industrial plants where a lot of machine noise is present, it may be useful to use radios as a way of communicating with coworkers located elsewhere in the plant. Because of the high noise levels, earphones must be worn to hear the radio communications. To be effective, the earphones must also block out some of the external noise. But if they block out too much of the external noise, the user will not be able to hear the conversations of nearby coworkers or the helpful sound queues of operating machinery. In airplanes, the airline pilot needs headphones that effectively block out the external engine noises. But the pilot also needs to hear the conversation of people who are nearby, such as their copilot or other airline support staff. In those applications, the around-the-ear headphones sometimes can cause unacceptable degradation of intelligibility of the conversations of such people.
The on-the-ear headphone, which is also referred to as the supra aural design, has an earphone cushion that simply rests against the ear when the headphone is being worn by the user. Typically, the cushion is made of an open cell foam material that easily transmits sound. This design tends to be lightweight, compact, and very comfortable. One disadvantage, however, is that conventional on-the-ear designs do not very effectively attenuate external noise. Thus, they are not well suited for use in noisy environments.
The in-the-ear headphone which typically provides less attenuation than the around-the-ear type has an ear piece that fits into the ear cavity, i.e., concha. Unlike the around-the-ear design, however, the in-the-ear headphone is typically very light and compact and thus for that reason it can be very comfortable to wear.
In general, in one aspect, the invention is an in-the-ear headphone including an earphone which is placed onto a user""s ear. The earphone includes a shell body defining an internal cavity. The shell body has an extended portion shaped and sized to fit into a concha of the user""s ear. The extended portion includes an aperture at an end thereof which aligns with the user""s ear when the earphone is being worn by the user. The extended portion defines a passageway extending from the aperture to the internal cavity so that the internal cavity is acoustically coupled to the user""s ear cavity when the headphone is being worn by the user. The earphone also includes a cushion covering at least part of the extended portion of the shell body and having an opening aligned with the aperture. The cushion may be made of a molded, self-skinned material.
Preferred embodiments include the following features. The cushion is made of a damped, compliant material and it includes bulbous portions near the opening and surrounding at least some of the aperture. The bulbous portions are in a range of about 3 to 5 millimeters in thickness. The internal cavity has a total volume that is larger than 10 cubic centimeters (e.g. 20 cc.). The aperture is oval-shaped and has dimensions of about 3 to 3.5 mm by about 8 to 10 mm. (i.e., it has an area that is between 25 to 35 mm2). The earphone further includes an acoustic damping material within the internal cavity (e.g. an open cell foam).
In general, in another aspect, the invention is an in-the-ear headphone including an earphone which is placed onto a user""s ear. The earphone includes a shell body defining an internal cavity. The shell body has an extended portion shaped and sized to fit into a concha of the user""s ear. The extended portion includes an aperture at an end thereof which aligns with the user""s ear when said earphone is being worn by the user and it defines a passageway extending from the aperture to the internal cavity so that the internal cavity is acoustically coupled to the user""s ear cavity when the headphone is being worn by the user. The earphone also includes an acoustical driver mounted within the extended portion; and an acoustical microphone mounted within the extended portion. The microphone is located substantially between the driver and the aperture and near a lower edge of the aperture.
In preferred embodiments, the aperture is oval shaped and has a long axis and a short axis and the plane of the driver is substantially parallel to the long axis of the oval-shaped aperture. The aperture is oriented so that its long axis is oriented vertically when the earphone is worn by the user. Also, the plane of the driver and the plane of the aperture are oriented at an angle of between 45xc2x0 and 90xc2x0 with respect to each other. The earphone also includes a hollow tower structure within the shell body. The tower structure holds the driver within the earphone and defines a rear cavity behind the driver. The rear cavity is separate and substantially isolated from the internal cavity. The rear cavity has a volume that is substantially smaller than the volume of the internal cavity (e.g. 2 cubic centimeters). A wall of the rear cavity is formed by a section of the shell body and it includes a second aperture connecting the rear cavity to outside of the shell body. The said second aperture is covered by a material having an acoustic resistance. The tower structure includes a pressure equalization hole connecting the rear cavity to the internal cavity. The pressure equalization hole has a diameter of less than about 1 millimeter (e.g. 0.25 and 0.5 millimeters).
Also in preferred embodiments, the plane of the microphone is substantially perpendicular to the plane of the driver and the plane of the microphone forms an angle with the plane of the aperture of between 45xc2x0 and 60xc2x0.
The in-the-ear headphone of the invention protects a user""s ears by actively and passively attenuating external noise, which leaks into the users ear canal when the headphone is worn by the user, such that the total attenuation of the system is relatively flat across the audible frequencies. Total attenuation of better than about 15-25 dB is achievable with the invention. It has been shown that 20 db attenuation is sufficient for good hearing protection and yet it still enables people to hear each other when communicating in an industrial environment.
Other advantages and features will become apparent from the following description of the preferred embodiment and from the claims.